This invention concerns a drilling device for brittle materials with a drill head detachably fixed to a drilling rod by means of a positive-lock connection.
In practice, such drilling devices are used for drilling glass materials for example. The inherent basic conditions differ so fundamentally from those for processing metallic materials that the use of the same drilling devices is largely precluded. Firstly, an adaptation of the drill head is required to prevent undesirable damage to the brittle material, the drill head usually having several graduated drill bits differently dimensioned in their diameter. Also, the connection between drill head and drilling rod is to be adapted to the special circumstances in the processing of brittle materials. There are two basic objectives faced with this: on the one hand, accurate guiding of the drill head should be realized and thus a close tolerance processing of the material; on the other hand, simple handling of the drill head is to be realized as well.
It is already known from DE-GM 19 13 317 to connect the drill head with the drilling rod by means of a slot and feather design. However, such design of the connection can only insufficiently meet the requirements on the drilling device in terms of the required precision. In particular, it will be disadvantageous thatxe2x80x94for the simple replacement of drill bitsxe2x80x94a measure of tolerance must be provided for between their boring and the drilling shaft which will inevitably result in deviations of nominal values during the drilling process.
DE 44 34 025 A1, in contrast, shows an altered connection where the drilling rod is screwed on by means of a corresponding thread for fixation of the drill head. In this case, the drill head is aligned by two cylindrical bearing areas, as well as a front stop. Here too, a tolerance measure is to be provided for easy mounting which can result in imprecisions in the drilling process, especially in terms of the comparatively extravagant structure of the drill head and the increased requirements in the processing of brittle materials. Moreover, the screw connection requires considerable expenditure in maintenance and care to prevent premature wear, caused by grainy particles of material which can lead to deposits and thus to damages on the drill head surface.
For increasing the precision to be achieved, it might be conceivable to employ a connection well-proven in metal processingxe2x80x94a chuck for example. However, this will fail in the processing of materials which tend to produce chippings which cannot be comparatively easily removed; it may also fail because of damage to the connection due to deposits or penetrating particles, thus precluding any reliable continuous use.
Before this background, the invention is based on the task to provide for a connection between the drill head and the drilling rod which on the one hand allows for high accuracy in processing the material, and on the other hand for easy handling. Especially, any premature wear of the connection is to be precluded.
This task is met by a drilling device according to the characteristics of Patent claim 1. The sub-claims concern especially favorable embodiments of the invention.
According to the invention, a drilling device is provided in which the positive-lock connection between drill head and drilling rod is designed for a reliable transmission of the drilling torque, while an essentially conical shape is provided and insertable into a corresponding receptacle for centric positioning of the drill head on the drilling rod. Thus the drill head, independent of the transmission of the drilling torque, is positioned and centered with high accuracy by means of the conical shape, the drilling torque being transmitted by the positive-lock connection. Accordingly, no thread is required for fixing the drill head, and even comparatively large tolerances do not affect the accuracy of the subsequent drilling process, as the drill head is positioned exclusively by the conical shape. Thus, handling is greatly simplified so that the expenditure on changing the drill head as well as the downtimes of the drilling device in the manufacturing process can be significantly reduced. At the same time, the expenditure on care and maintenance is reduced as the design of the positive-lock connection minimizes the influences of material chippings also in permanent operation. The cleaning of the conical shape, if required, is simple as there are no moving components or undercuts.
In an especially favorable embodiment of the drilling device according to the invention, the positive-lock connection is formed by at least one projection connected with the drill head and by a recess of the drilling rod, the recess accepting the projection. Thus, such a projection, designed for example as a cam, engages in positive-lock into the recess of the drilling rod on fixing the drill head, thus reliably transmitting the drilling torque. Any tolerance measures between recess and drilling are not harmful here, as the contact areas between drilling head and drill rod automatically rest against each other on operation of the drill head. Accordingly, feeding devices designed for example as a chamfering device can be provided for further simplified execution of the connection.
In a simple embodiment of the connection, the positive-lock connection has a claw coupling. Such a connection, also available as a standard component, allows for simple installation and a reliable use of the drilling device in practice. For this purpose, the claw coupling has for example at least two immobile or even mobile claws arresting automatically in operating position, thus preventing any undesirable axial release of the drill head from the drilling rod, for example on drawing the drill head back from the drilled hole.
Another favorable embodiment of the invention serves this purpose especially well as the drilling device features an arrest as a protection against any undesirable relative axial mobility between the drill head and the drilling rod. Here, this arrest or fixing device primarily protects the projection and the recess from getting out of contact, in which case the reliable transmission of the drilling moment is no longer guaranteed. Thus, the arrest, designed for example as a catching or clamping device, serves to protect the connection between drill head and drilling rod to prevent any loosening of the connection. Also stopping bodies designed as a wedge, or a locking pin penetrating the connection are conceivable.
In another especially favorable embodiment of the invention, the arrest has a sleeve which engages into a thread of the drill head or into a thread of the drilling rod. Subsequent to the connection of the drill head and the drilling rod, the sleeve allows them to be non-positively braced against each other, precluding any incidental loosening. At the same time, the sleeve designed as a hollow nut encloses the connection, thus allowing for sealing or at least for improved protection against any penetrating particles. Here, the sleeve is arranged freely rotatable either at the drill head or at the drilling rod, with limited axial mobility in the direction of the respective remaining component. For fixing, the sleeve is slipped over the connection, engaging by rotation into the respective thread, the opposite end of the sleeve sitting against a stopper.
In another especially practical embodiment of the invention, the arrest simultaneously engages into a thread of the drill head and into a thread of the drilling rod, with the two threads having countercurrent pitches. By the arrest thus engaging into the countercurrent threads, the drill head can easily be braced against the drilling rod, a good sealing effect and thus an improved protection of the connection enclosed by the arrest being achieved as well. To disengage the connection, the arrest is simply rotated into the opposite direction, drill head and drilling rod being separated. In this way, the disengagement is comparatively effortless even if the connection has to be disengaged against the adhesive powers of deposited particles.
The arrest can have a cross section with a polygonal outside surface allowing for application of a commercially available tool for realization of the necessary rotary movement. In an especially recommendable embodiment of the invention, the arrest has on the outside at least one depression running over the entire axial distance. In this way, this depression at the same time allows for unimpeded flowing of the drilling fluid along the depression serving as a channel. Simultaneously, a tool engaging into the depression can be used to create the rotary movement. The depression can run either primarily parallel to the drilling axis, or it can be slant or arranged in a spiral, which also assists the flow of the drilling fluid. By a multitude or depressions, the advantageous effects are enhanced.
In another especially practical embodiment of the invention, the arrest is arranged recessed versus the outside radial dimensions of the drill head. In this way, the flow of the drilling liquid is only insignificantly affected, and contact of the arrest and a wall space of the drilled hole and a respective potential damage to the arrest or the wall space is avoided.
Furthermore, it is especially favorable when the arrest has a form element covering coaxially a depression arranged on the circumference of the drill head respectively the drilling rod so that a hollow space is formed which will prevent any axial displacement between drill head and the drilling rod by filling it with obstructing bodies, especially balls. For this purpose, the drill head or drilling rod require merely a depression designed as a groove, while the fixing device or arrest equipped for axial fixing is provided with a corresponding guiding strip for the obstructing bodies. The arrest created in this way also allows for retrofitting of already existing drilling devices.
In an especially simple embodiment of the invention, the arrest is designed as a union nut. This union nut can for example be arranged on the drill head freely rotatable and fixed in axial direction, so that after locking of the connection, the drill head can be axially fixed by simply screwing the union nut on the a thread of the drilling rod. In this way, the expenditure for manufacture and for handling when exchanging drill heads can be further reduced.
In another especially favorable embodiment of the invention, the arrest is designed in such a way that the drill head has a first form element which in operating state together with a second form element of the drilling rod limits a hollow space which, when filled with obstructing bodies, especially balls, will prevent any axial displacement between drill head and the drilling rod. Thus, a simple axial fixing or arrest of the drill head to the drilling rod is achieved which can be handled effortlessly, while the fixing device is designed as an integral part of the drill head and the drilling rod so that no additional component is required. Here, the hollow space is filled with obstructing bodies through a lockable opening, so that any axial displacement of the drill head versus the drilling rod is blocked by means of the two form elements essentially covering each other, while a relative rotation of the drill head versus the drilling rod is not be precluded. Accordingly, the drilling torque is transmitted exclusively by a positive-lock connection. Embodiments are also conceivable in which by introduction of the obstructing body, any axial displacement is prevented and simultaneously the transmission of drilling torque is made possible.